Down-hole oil field equipment which is electrically operated requires the use of a cable extending from the surface generating equipment through the well casing to the down-hole equipment. Armored electrical cable is employed to deliver the current to operate the down-hole equipment, for example a motor and pump. The electrically driven apparatus, such as a submersible pump, is attached to the lower end of the production tubing, i.e., the tubing string, and the entire assembly -- the electrical motor, the submersible pump, and the tubing string, are lowered into the well from the surface. The electrical cable is supported by the tubing string by means of a narrow band of rolled steel which is wrapped around the tubing string and cable at approximately 10 foot intervals, and tightened to secure the cable to the tubing then sealed or locked in the tightened position by mechanically crimping the steel band or strap and holding the crimped section with a seal. The banding or strapping procedure and equipment is well known in the art.
In the past there have been numerous instances of electrical failure in the cable used in the foregoing manner, due to stretching of the cable. Stretching is on the order of about one inch per foot in some cases which is often sufficient to cause electrical failure. The cost of the cable replacement in the event of such a failure and the lost time involved in such replacement is very expensive.
Another source of electrical failure involves the snagging of the banding or strapping used to secure the cable to the tubing, on the inside edge of the casing joints at the gap between joints. Such snagging can result in tearing the strapping at the joints and damage to the cable. This problem is particularly prevalent in slant-hole operations where the tubing and cable assemblage, bear against the inside surface of the casing as the cable is lowered through the casing with the tubing.
It is an object of our present invention to provide an improved means and method for strapping the electrical cable to the production tubing for lowering into a well.
It is a further object of our present invention to provide strapping for securing an electrical cable to a tubing string for lowering into a well, which minimizes the stretching and elongation of said cable by the weight of said cable and decreases the friction on the cable while sliding downhole in contact with the inner surface of the well casing, for example in a slant hole.
It is also an object of our present invention to provide metal strapping for securing an electrical cable to a tubing string, which will not snag on the casing joint ends as said cable and tubing are lowered down through the casing.
These and other objects of our invention will become apparent from the following description of the invention and from the appended claims and the drawings.